The present invention relates to an electrical device.
European Published Patent Application No. 0 722 624 describes an electrical device which has a first and a second housing part, which together form a closed housing. Arranged in the housing is a circuit element that is configured as a printed-circuit board, supporting elements configured in the first housing part penetrating through-openings in the printed-circuit board. The support elements are configured so that the printed-circuit board moves in the direction of the first housing part when the second housing part is mounted, and a sealing material, arranged between the printed-circuit board and the first housing part, is subjected to compression and is squeezed into a position in which it forms a circumferential bulge on the side walls of the housing and as a result seals the contact area of the two housing parts. In the housing part that is sealed in this manner, a hollow space filled with air remains between the printed-circuit board and the second housing part. Retaining elements that are configured on the second housing part prevent the printed-circuit board, once it has arrived in its final position, from being pressed back into the hollow space by the compressive force of the compressed sealing material, as a result of which the sealing bulge would be pulled away from the housing walls. One disadvantage in such a device is that the printed-circuit board must be provided with openings for the supporting elements, and therefore space is lost on the printed-circuit board for the arrangement of electrical and/or electronic components. In addition, electrical connecting leads cannot be fed into the housing interior through the bulge-like seal between the housing parts, and therefore must be fed, in a cumbersome manner, through a separate passage in one of the two housing parts into the housing interior. This passage also must be sealed off, requiring additional expense. Harmful gases in the enclosed hollow space above the printed-circuit board can impair the mode of functioning of the electronic components on the printed-circuit board.
As a result of the electrical device according to the present invention, the foregoing disadvantages that may arise may be avoided, and reliable protection from harmful environmental influences is made possible for a circuit element arranged in a housing. The device assures a sufficient seal of the circuit element with respect to spray water, humidity, or submersion in water. The device is both simple as well as economical to manufacture and has two half-shells, the interior area of which in each case is subdivided by interior walls into at least two chambers, of which a first chamber is filled with sealing material, e.g., a gel, and has spatial dimensions that are larger than the dimensions of the circuit element. In the joined state of the two half-shells, the interior walls of the second half-shell overlap, with clearance, the inner walls of the first half-shell, as a result of which it is achieved that the sealing material contained in the two half-shells comes into contact around the circuit element in a frame-like, circumferential area, merges together, and thus seals off the circuit element circumferentially. Due to tolerances in the housing dimensions, tolerances in the pouring of the sealing material, and a shrinking process in response to the hardening of the sealing material, the sealing material poured into the first chambers before the assembly of the two half-shells forms a meniscus, so that the surface of the sealing material in the two chambers is curved in a concave manner and contacts the upper edges of the inner walls, although in the center of the chamber it recedes somewhat towards the interior. This may not be avoided in a simple manner and, without taking countermeasures, results in hollow spaces arising above and below the printed-circuit board when the two half-shells are joined together, due to the concave curvature. In order, when the two half-shells are joined together, to prevent a faulty seal of the edge area of the printed-circuit board from arising as a result of an insufficient pressure of the sealing material in the edge area of the printed-circuit board, resulting from the presence of the hollow spaces, it is provided that the interior walls of the first half-shell, when the two half-shells are joined, penetrate somewhat into the first chamber of the second half-shell. As a result, it is achieved that the first chambers of the half-shells, engaging one another, form an overlapping area, a sufficient quantity of sealing material being pressed out of the overlapping area when the half-shells are joined in order that the edge area of the circuit element be enveloped in sealing material circumferentially in a sufficiently reliable manner. In this manner, it may be achieved that the circuit element between the two half-shells is encased up to its electrical leads by the sealing material contained in the two first chambers, i.e., it is arranged so as to be encapsulated in the sealing material.
Example embodiments and refinements of the present invention are described below.
The interior area of each half-shell may be subdivided, by two interior walls, extending parallel to each other, which join to each other two side walls of the half-shells facing each other, into a first chamber arranged centrally and two second chambers laterally adjoining the first chamber. The second chambers provided in each half-shell function, inter alia, as the receiving areas for excess sealing material that is squeezed out of the first chambers when the two half-shells are joined together. As a result of the distance between the interior walls of the first and the second half-shells, a drainage channel is formed for the sealing material that is squeezed out of the first chambers, which is able to escape via the drainage channel into the second chambers.
The half-shells may be joined to each other, e.g., using a detention arrangement. When the two half-shells are joined together, larger quantities of sealing material are compressed and are squeezed out of the overlapping area of the first chambers. Without a joining arrangement, the strong compressive forces resulting from the compression may force the two half-shells apart. The detention arrangement may therefore be able to withstand larger forces. The detention arrangement, arranged on one half-shell, may include detent hooks having barbed-shaped latches, the hooks, in each case, engaging in a guide slot arranged on the other half-shell and which, in each case, gripping from behind, using their latches, a projecting part arranged in the guide slot. The guide slots protect the latches, so that an unintentional unlatching of the latches is not possible. In particular, the width of each guide slot and the geometrical dimensions of the corresponding latches may be adjusted to each other, so that a latch engaging in a barbed-like manner behind the projecting part may no longer be detached from its latched position without being destroyed.
The side walls of the half-shells may have cutouts, which in the joined state of the housing part, form openings between the two half-shells for the feeding through of the electrical connecting leads. When the two half-shells are joined, the connecting leads extending through the openings to the outside are embedded in the sealing material.
A strain relief device may be provided on at least one half-shell for the electrical connecting leads.